- P-ISSN 1225-0163
- E-ISSN 2288-8985
Tyrosinases are related to the enzymatic browning of plants and attract the major scientific interest for the prevention of it. Three tyrosinase isozymes (<TEX>$P_1$</TEX>, <TEX>$P_2$</TEX> and <TEX>$P_3$</TEX>) from pine needles were purified to homogeneity and characterized the factors that affect their activities. The L-ascorbic acid and <TEX>${\beta}$</TEX>-mercaptoethanol notably inhibited the enzymatic activities of the three isozymes. The sodium diethyldithiocarbamate was a competitive inhibitor of isozymes with the <TEX>$K_i$</TEX> values of <TEX>$P_1$</TEX>(0.030 mM), <TEX>$P_2$</TEX>(0.015 mM) and <TEX>$P_3$</TEX>(0.019 mM), respectively. Their enzyme activities were however, increased by the addition of most metal ions. The optimum pH for the three isozymes was 9.0~9.5 and the optimum temperatures ranged from 55 to <TEX>$60^{\circ}C$</TEX> using L-DOPA as substrate.